Fabrication of integrated circuits (IC) typically involves one or more steps performed in vacuum process chambers, where material processing (e.g., deposition and/or etching) is performed at subatmospheric pressure. For example, many metals and metal nitrides are deposited onto a wafer substrate by sputtering in a PVD process chamber, usually in a plasma-assisted iPVD process. Many dielectric materials are deposited in a chemical vapor deposition (CVD) process chamber, e.g., in a plasma enhanced chemical vapor deposition (PECVD) chamber, high density plasma chemical vapor deposition (HDPCVD) chamber, low pressure chemical vapor deposition (LPCVD) chamber, and the like. Further, many etching processes are performed in vacuum process chambers, e.g., in chambers adapted for plasma etching and reactive chemical etching.
During deposition and/or etching, the components of the chamber, such as chamber walls, sides of wafer pedestal, and wafer chuck are protected from unwanted deposition of material by a shielding system which includes one or more shields configured to accept the unwanted flux (over-spray) of the deposited material. As a result, little or no deposition occurs on protected surfaces of the chamber, while a layer of material builds up on the shields.
Process chamber shields often have generally cylindrical shapes or other shapes that generally follow the geometry of protected surfaces. The shields are typically mounted to a chamber element (e.g., chamber wall, or wafer pedestal) at one end, and have a distal end freely terminating within the interior space of a process chamber. In addition to a general shape, the shields may have a variety of locally shaped portions, e.g., concave portions, convex portions, S-shaped portions, etc., which are used to optimize chamber surface protection. In some embodiments, generally flat shields may be employed.
Process chamber shields can be used for a certain amount of time without cleaning or replacement. Typically, the shields are used until the layer of material deposited on their surface becomes too thick to be supported by the shield and begins to flake or delaminate thereby leading to contamination. Periodic preventive maintenance requirement (PM) also limits the time over which shields can be used continuously. Flaking may lead to substrate contamination resulting from undesired release of loose particles on the substrate. Shortly before substantial flaking starts to occur, the shield is typically replaced with a new shield or is cleaned to remove the layer of deposited material, and is then re-installed into the process chamber.
Shields, particularly shields having complex shapes, are often expensive. Further, re-installation of a shield system in a deposition chamber can also be a costly procedure. Accordingly, it is highly desirable to provide shielding systems with increased lifetime to minimize costs of IC fabrication. Specifically, it is desirable to provide shields which would be able to support thicker films on their surfaces without film flaking or delamination.